1. Field of the Invention
The present invention relates to an apparatus for compensating a digital video signal.
2. Description of the Related Art
Recently, with development of a technique for processing a digital video signal and improvement of a display device of the digital video signal, it is general tendency that display devices have large sizes. Such a tendency of a large sized display device will be continued in accordance with increase of resolution and development of additional technologies when displaying a digital video signal.
Meanwhile, a current projection television receiver does not have excellent resolution. However, if a digital television receiver is popularized in accordance with its transmission and reception technologies, a video of high resolution can be displayed in the projection television receiver. In this respect, it is expected that the projection television receiver will receive much attention as a digital television receiver as a larger sized screen is required.
FIG. 1 is a block diagram showing a general structure of a display device.
Referring to FIG. 1, a video processor is based on both an analog mode and a digital mode. Recently, it is general that the video processor is implemented based on the digital mode.
Meanwhile, a display processor serves to directly display a digital video signal on a screen. The display processor of the projection television receiver is currently implemented based on the analog mode.
As described above, since a related art projection television receiver includes a display processor provided with an analog circuit, a digital video signal fails to be displayed at an original brightness level in each pixel position of the screen. In other words, brightness of the screen is varied depending on a viewing angle of a viewer of the projection television receiver. As an example, the displayed digital video signal is bright at the center of the screen while it becomes dark toward the periphery of the screen from the center thereof. This is also shown in case that a brightness value of the screen is actually measured for each area. That is, the brightness value of the screen is varied depending on positions on the screen, i.e. the center of the screen and the corner portion of the screen.
FIG. 2 is a diagram showing a brightness value variation of the digital video signal according to the positions on the screen when a full white video signal is displayed on the screen. Referring to FIG. 2, when the digital video signal is displayed, a video displayed on the screen of a two-dimensional screen has different brightness values depending on the positions on the screen.
Generally, all of the display devices have the highest brightness value at the center of the screen and the lowest brightness value in the periphery of the screen. Accordingly, the periphery of the screen is darker than the center.
As described above, the related art projection television receiver has different brightness values depending on the number of electron guns, the distance between the respective electron gun and the screen, and the coordinate position of the screen.
This is because that the distance between the respective electron gun and the screen is varied and it is difficult to exactly set a focus of electron beams for R, G, and B with respect to each point of the screen.
The difference of brightness on the screen occurs seriously in the projection television receiver. Particularly, the difference of brightness is more serious as the screen size of the projection television receiver becomes larger. As an example, for a large sized projection television receiver, a brightness difference of 30% or greater occurs at the center of the screen and the corner portion thereof.
To solve the above problems, an object of the present invention is to provide an apparatus for compensating a digital video signal in which a brightness value of each pixel is compensated before the digital video signal is displayed.
Another object of the present invention is to provide an apparatus for compensating a digital video signal in which the uniform distribution of brightness is maintained on a whole screen when displaying a digital video signal.
Other object of the present invention is to provide an apparatus for compensating a digital video signal in which a hardware construction is easily implemented.
To achieve the above object, an apparatus for compensating a digital video signal according to one aspect of the present invention is characterized in that a linear distance function is obtained between a center pixel and each pixel on a screen consisting of x coordinates and y coordinates.
An apparatus for compensating a digital video signal according to another aspect of the present invention is characterized in that a shade reflection ratio of each pixel is calculated per display clock using the linear distance function, and brightness of each pixel is adjusted by the shade reflection ratio.
An apparatus for compensating a digital video signal according to another aspect of the present invention includes a shade reflection ratio calculator for calculating a shade reflection ratio of each pixel per display clock, using a linear distance function between a center pixel and a current pixel on a screen. The apparatus according to another aspect of the present invention also includes a brightness compensator for compensating brightness of each pixel corresponding to an input digital video signal using the shade reflection ratio value r and an externally provided brightness adjustment range Yrate.
In the preferred embodiment of the present invention, brightness of a digital video signal is compensated by a digital video signal processor before the digital video signal is displayed on a screen, so as to decrease brightness difference between the center of the screen and the periphery thereof. Thus, load of the analog display processor is reduced, thereby improving picture quality of the displayed video.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.